Drying apparatus



June 2, 1964 D. E. STOKES DRYING APPARATUS Filed Sept. 29, 1961 INVENTOK DAVID E. STOKES ATTORNEY" a g -wr United States Patent Filed Sept. 29, 1961, Ser. No. 141,838 3 Claims. (Cl. 34-73) This invention relates to a drying apparatus, and more particularly, an apparatus within which articles may be vacuum dried or freeze dried.

Industry is making wide use of freeze-drying techniques and vacuum drying techniques in the preparation of many products. Freeze drying is being utilized for the processsing of many articles such as extracts, citrus juices, meats, milk, blood, bones, etc., so that they may be stored indefinitely without refrigeration. Modern processing of such articles is being accomplished without impairment or loss of natural flavor, vitamin content or quality.

To supplement the wide use which is being made by Patented June 2, 1964 It is still another object of the present invention to provide a vacuum drying apparatus having heated shelves and a condenser means all disposed within a single housing.

It is a further object of the present invention to provide' a vacuum drying apparatus proportioned in a manner so as to provide maximum efiiciency and compactness so that said apparatus may be utilized for laboratory test purposes.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawing a form which is presently preferred;

I it being understood, however, that this invention is not industry, a large amount of research is being done. In

order to facilitate such research, there is a, need for a small laboratory type drying apparatus so that additional research may be accomplished. Heretofore, vacuum drying apparatus and freeze drying apparatus have been to. an extent large, bulky, and expensive. In order to utilize a large number of the freeze drying and vacuum drying devices proposed heretofore, it was necessary for a user to have sufiicient floor space so as to accommodate the freeze drying apparatus and the large condenser associated therewith as well as a supply of steam or other motive fluid for heating the shelves within the apparatus.

The drying apparatus of the present invention is primarily designed for use in laboratories and the like. The apparatus of the present invention is small, compact, and is primarily designed so as to have electrically heated shelves and electrically operated condenser means all disposed within a single housing. In this manner, theapparatus of the present invention will provide shelves which may be almost instantly heated when desired as well as a condenser means which may perform its intended function more rapidly.

i The shelves within the housing of the apparatus of the present invention are preferably a rigid heat resistant non-conductive sheet of material having an electrically conductive coating on opposite surfaces thereof. The electrically conductive coating is preferably covered with a non-conductive film such as lacquer. A spacer device is provided so as to space trays of articles from the shelves whereby such articles will be heated by radiant heating. The condenser means includes a pair of thermoelectric plates coupled to a source electricity in a manner whereby the polarity of the current connected thereto may be reversed so that the plates are cold when acting as a condenser and hot when moisture frozen thereon is being melted.

It is an object of the present invention to provide a novel drying apparatus.

It is another object of the present invention to provide a novel vacuum drying apparatus.

It is another object of the present invention to provide a novel vacuum drying apparatus having electrically heated shelves.

It is another object ofv the present invention to provide a vacuum drying apparatus having electrically heated shelves which are readily removable for cleaning purposes.

It is still another object of the present invention to provide a vacuum drying apparatus with a thermoelectric condenser means.

limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a perspective view of the apparatus of the present invention with portions broken away for purposes of clarity.

FIGURE 2 is a longitudinal sectional view taken along the lines 2-2 in FIGURE 1.

FIGURE '3 is an enlarged partial perspective view showing the manner in which the shelves are to be electrically coupled when mounted.

FIGURE 4 is an enlarged partial perspective view of the condenser means.

Referring to the drawing in detail, wherein like numerals indicate like elements, there is shown in FIGURE 1 a drying apparatus designated generally as 10.

The drying apparatus 10 comprises a vacuum tight housing 12 which may be insulated if desired. The housing 12 is provided with an access opening selectively closed by means of a pivotably mounted door 14. The interior of the housing 12 is adapted to be evacuated so that drying may take place under vacuum. Thus, a vacuum pump 16 is connected to the interior of the housing 12 by means of a conduit 18. The conduit 18 communicates with the housing 12 adjacent the bottom portion thereof.

The housing 12 includes oppositely disposed side walls 20 and 22. A plurality of brackets 24 are fixedly secured to the inner surface of the walls 20 and 22 at spaced points above one another. Shelves 26 are horizontally supported by means of the brackets 24. While only two shelves 26 are illustrated, the number of such shelves may be increased as desired. Each shelf 26 includes a rigid heat resistant non-conductive layer of material having a coating of electrically conductive material 28 on opposite surfaces thereof. The coating of conductive material 28 is preferably covered with a film of electrically non-conductive material such as lacquer. The brackets 24 are preferably electrically non-conductive.

' The shelves 26 are disposed above one another within the housing 12 between an upper shelf 32 and a lower shelf 33. The shelf 32 is provided with a coating of conductive material 34 on a bottom surface thereof. The coating of conductive material 34 is identical with the coating of conductive material 28 and is preferably covered with a film of non-conductive material such as lacquer. The shelf 33 is identical with the shelf 32 except that the coating of conductive material 34 is disposed on the upper surface thereof. In this manner, it will be seen that trays of articles disposed on the shelves 26 between the shelves 32 and 33 will be subjected to radiant heat from above and below.

Each of the above mentioned shelves are proportioned so that their side edges are spaced inwardly from the inner peripheral surfaces of the housing 12. A layer of heat insulating material 36 is supported by brackets 38 below shelf 33. The layer 36 is proportioned so that its side edges are spaced inwardly from the inner peripheral surfaces of the housing 12. Such spacing of the shelves in series.

sitionadjacent the back wall of the housing lZ, The

electrical conduit 40, per se, is of conventional construction and includes female sockets .42 at spaced points therealo'ng. The shelves 26, 32 and33 are provided with male socket members 44 extending therefrom. The

coating of conductive material on the shelves 26, 32 and 33 is electrically coupled to the male socket members. A'

greater number of female sockets 42 than the number of shelves may be provided so that the spacing between the shelves may be varied as desired.

The electrical conduit 46 is connected to a switch 46 on of the housing 12 is provided with a centrally disposed concave portion 60; A drain pipe 62 extends from the V concave portion 60 through the bottom wall of the housing 12. The purpose of the pipe 62 will be made clear hereinafter. A thermoelectric condenser means 64 is disposed between the bottom wall of the housing 12 and the layer 36.

As shown more clearly in FIGURE 4, the condenser means 64 includes a pair of spaced substantially parallel heat absorbing plates 66 and 68. As will be made clear hereinafter, the plates 66 and 68 are electrically coupled An N-type thermoelectric element 70 and a P-type, thermoelectric element 72 extend from the plate 66. Element 76 is connected to a heat transfer fin 74. Element 72 is connected to a heat transfer fin 76. An N-type thermoelectric element 78 extends from the plate 68 to a heat transfer fin 80. The heat transfer fin 80 is disposed intermediate the fins 74 and 76. A P-type thermoelectric element 82 extends from the plate 68 to a heat transfer fin 84. The plates 66 and 68 operate as cold junctions when current is flowed therethrough in a proper direction. Elements 72 and 78 are electrically coupled together by means of a metallic strip 86. The metallic strip 86 functions as a hot junction. A male socket member 88 extends from the fin 84 and a male socket member 9tlextends from the fin 74. The members 88 and 90 are adapted to cooperate with female sockets on a rectifier 92, per se, of conventional construction. The condenser means 64 is supported by brackets 94 on theside walls 20 and 22 of the housing 12.

The operation of the apparatus has follows:

. It will be assumed that it is intended to use the appara- -.tus 10 to freeze dry articles, such as the above mentioned articles.

Such articles will be disposed within trays 96 and disposed within a freezer until such articles are frozen. Then the trays 96 are transferred to the apparatus 10 and placed on spacers 98 which rest upon the shelves 26 and 33. The trays 96 may be provided with perforated bottoms so as to provide for ease of escape of vapors. The spacers 98 locate the bottom of the trays 96 in a position so that the articles within the trays 96 Will be heated by radiant heat from above and below. Thereafter, the vacuum pump 16 will be initiated so as to evacuate the interior of the housing 12. At the same time, the switch element on the switch 46 will be manipulated to an on position so as to enable current to flow to the coating of conductive material on the shelves. Such current will also flow to the rectifier 92 wherein direct current will be flowing from the rectifier 92 through the fin 74, element 70, plate 66, element 72, strip 86, element 78, plate 68, element 82 and fin 84 back to the rectifier 92 in that sequent. With the current flowing in this direction through the alternate thermoelements and sulting moisture will readily flow through the passageway provided between the side edges of the shelves and layer 36 and the inner peripheral surfaces of the housing l2. Such moisture will be condensed by the plates 66 and 63. Any liquid condensate will be drained through the pipe 62. When the predetermined amount of moisture has been removed from the articles, the pump 16 may be stopped and the switch element manipulated to an off position. Thereafter, the door 14 may be opened and the trays 96 removed therefrom. Thereafter, the switch element on the switch 46 may be manipulated to its other on position thereby reversing the polarity of the current supplied to the trays and thermoelectric condenser means' The spacing of the'female sockets on the electrical conduit 42 accommodates the drying'of various sized articles. Large articles may also be'accommodated by'removing one of the shelves 26 if desired. The repetition Y with which the shelves may be heated and the compact nature of the apparatus It enables the apparatus 10 to be suitably adapted for laboratory purposes. electric means 64 enables a condenser to be provided in the same housing as the heater shelves. Heretofore, it was conventional to provide the condenser in aseparate housing of a size comparable to the size of the housing containing the heater shelves. Thus, in order to use the apparatus 16 of the present invention, only a source of electrical potential and an outlet for the drain pipe 62 are required.

The material of the rigid electrically non-conductive heat resistant shelves and coating of electrically conductive material thereon, per se, form no part of the present utilized as a drying apparatus, it Will be appreciated by those skilled in the art that the operation of the same is identical as set forth above except that the articles will i not be in a frozen state when inserted within the housing 12. While the apparatus 10 has been disclosed with spacers 98 between the trays 96and the shelves, it will be appreciated that the spacers 98 may be eliminated if desired. Also, it will be appreciated that the coating of electrically conductive material on the shelves is electrically isolated from the supporting brackets for the shelves and the housing 12 as well as other elements so as to prevent short circuiting of the same. While the electrically heated shelves have been disclosed as being in the nature of planar sheets having coatings of electrically conductive material thereon, it will be appreciated that equivalent devices may be substituted therefor so long as they conform to the nature and environment of the shelves as disclosed. The particular material of the layer 36 forms no part of the present invention. The layer 36 should be made of any heat resistant insulating material capable of performing the function of preventing the plates 66 and 68 from being subjected to direct radiant heat from the shelves. While the shelves and condenser means are removably secured to the electrical conduit 4-0 by means of female sockets and male socket members, it will be appreciated that other equivalent devices may be substituted therefor.

The thermo-' The present invention may be embodied in other specific 2 forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

1 claim:

1. A drying apparatus comprising a housing having a drying chamber therein, said chamber including side, front and back Walls, said front wall having a door thereon,

' said back wall being opposite from said front Wall, means supporting a plurality of electrically heated shelves in said chamber, said shelves being coupled to a common electrical conduit, a thermoelectric condenser located below said shelves in said housing electrically coupled to said conduit, 21 heat reflecting and insulating shelf located betweentsaid thermoelectric condenser and said electrically heated shelves in said chamber, said heat reflecting I strip, and guide means on the side Walls of said housing supporting said electrically heated shelves and said thermoelectric condenser in a horizontal position with said electrically heated shelves and thermoelectric condenser mating contact members in alignment with said vertical strip mating contact members.

2. The drying apparatus of claim 1 wherein said thermoelectric condenser includes spaced substantially parallel heat absorbing plates disposed in substantially horizontal planes and a heat sink, said heat sink being located between said thermoelectric mating contact member and said heat absorbing plates, said vertical strip being adapted to be connected to a source of electrical energy, switch means on said housing connected to control the supply of electrical energy to said vertical strip, said switch means being capable of reversing the polarity of electrical current in said strip to heat said thermoelectric condenser.

3. The drying apparatus of claim 1 wherein said vertical strip is adapted to be connected to a source of alternating current, said electrically heated shelves being responsive to alternating current, and a rectifier mounted on said vertical strip adjacent said vertical strip mating contact member associated with said thermoelectric condenser to rectify current fed to said thermoelectric condenser through said last-mentioned vertical strip mating contact member and said thermoelectric condenser mating contact member.

References tCited in the file of this patent UNITED STATES PATENTS 2,132,897 Gentele Oct. 11, 1938 2,156,845v Gentele May 2, 1939 2,362,117 David Nov. 7,1944 2,389,452 Patterson Nov. 20, 1945 2,564,475 Fischer Aug. 14, 1951 2,602,825 Flosdorf July 8, 1952 3,008,300 Ryan Nov. 14, 1961 3,036,383 Edwards May 29, 1962 

1. A DRYING APPARATUS COMPRISING A HOUSING HAVING A DRYING CHAMBER THEREIN, SAID CHAMBER INCLUDING SIDE, FRONT AND BACK WALLS, SAID FRONT WALL HAVING A DOOR THEREON, SAID BACK WALL BEING OPPOSITE FROM SAID FRONT WALL, MEANS SUPPORTING A PLURALITY OF ELECTRICALY HEATED SHELVES IN SAID CHAMBER, SAID SHELVES BEING COUPLED TO A COMMON ELECTRICAL CONDUIT, A THERMOELECTRIC CONDENSER LOCATED BELOW SAID SHELVES IN SAID HOUSING ELECTRICALLY COUPLED TO SAID CONDUIT, A HEAT REFLECTING AND INSULATING SHELF LOCATED BETWEEN SAID THERMOELECTRIC CONDENSER AND SAID ELECTRICALLY HEATED SHELVES IN SAID CHAMBER, SAID HEAT REFLECTING AND INSULATING SHELF BEING SPACED FROM SAID SIDE WALLS TO PROVIDE A PASSAGEWAY FOR FLUIDS AND VAPORS WITHIN SAID HOUSING, A VACUUM PUMP IN COMMUNICATIONWITH SAID CHAMBER IN THE REGION OF SAID CONDENSER FOR SELECTIVELY EVACUATING SAID CHAMBER, SAID COMMON ELECTRICAL CONDUIT INCLUDING A VERTICAL STRIP MOUNTED ON SAID BACK WALL HAVING SPACED CONTACT MEMBERS THEREON, SAID ELECTRICALLY HEATED SHELVES AND SAID THERMOELECTRIC CONDENSER HAVING SPACED MATING CONTACT MEMBERS AT ONE END THEREOF ADAPTED TO MATE WITH SAID MATING CONTACT MEMBERS ON SAID VERTICAL STRIP, AND GUIDE MEANS ON THE SIDE WALLS OF SAID HOUSING SUPPORTING SAID ELECTRICALLY HEATED SHELVES AND SAID THERMOELECTRIC CONDENSER IN A HORIZONTAL POSITION WITH SAID ELECTRICALLY HEATED SHELVES AND THERMOELECTRIC CONDENSER MATING CONTACT MEMBERS IN ALIGNMENT WITH SAID VERTICAL STRIP MATING CONTACT MEMBERS. 